The present invention relates to a method of cooling a brake rotor and specifically for varying the angles of the vents in a rotor friction section to change the air flow through the vents for cooling the rotor.
Wheeled vehicles are typically slowed and stopped with a braking system that generates frictional forces. Many braking systems include a rotor attached to one or more of the vehicle wheels for rotation therewith, and a caliper assembly secured to a non-rotating component of the vehicle, such as the vehicle frame. The rotor includes an annular peripheral friction section having friction surfaces disposed on opposite sides. The caliper assembly includes a pair of brake pads disposed adjacent the rotor friction surfaces, and a moveable piston operatively connected to one or more of the brake pads. When the driver brakes the vehicle, hydraulic or pneumatic forces move the piston which clamps the pads against the friction surfaces of the rotating rotor. As the brake pads press against the moving friction surfaces, frictional forces are created which oppose the rotation of the wheels and slow the vehicle. The friction converts the vehicle's kinetic energy into large quantities of heat, much of which is absorbed by the friction surfaces and conducted throughout the rotor.
It is important to dissipate the heat and cool the rotor. If the rotor is not adequately cooled, the heat generated during braking can build up in the rotor reducing braking performance by creating longer stopping distances, shorten the life of the rotor, or even cause brake failure. The rotor also helps to keep the brake pads cool by absorbing the braking heat and moving it away from the pads. However, the rotor can only absorb a finite amount of heat and if it is not cooled effectively it will absorb less and less heat, causing the brake pads to overheat and thus reducing braking performance and shortening the life of the brake pads.
Rotors are commonly cooled using moving air which absorbs the heat from the rotor and carries it away. It is known to "ventilate" the rotors by forming passages or vents between the friction surfaces to allow cooling air to pass through. These ventilated rotors typically include friction surfaces formed on a pair of annular friction plates joined together by spacers or posts in a mutually parallel, spaced apart relationship to form spaces or vents therebetween. The vents are open at the radially inner and outer edges of the friction plates to form air passages between the friction plates. As the vented rotor turns, air moves through the vents between the friction surfaces and absorbs heat from the friction plates to cool the rotor.
The cooling effectiveness of the vents is proportional to the quantity of air moved through them. The more air the vents move past the rotor surfaces, the more heat that is dissipated and the greater the cooling effects. Therefore, it is desirable to move as much air as possible through the vents. The shapes, spacing and orientation of the posts determine the amount of air which passes through the vents. It is desirable to provide the optimum shape, spacing and orientation of posts to maximize the airflow through the vents.